Same Finish Inside and Outside?

I’m nearing completion on a large case piece with many drawers. From what I’ve read, it is as important to apply finish inside a piece as it is outside. My question is, can the finishes be different? I plan on applying tung oil and polyurethane on the outside but would like to apply shellac on the inside due to its fast-drying nature. Is this a common practice with past precedents? – Casey A. Blaze

Tim Inman: There was good research done on this very question back in the early 1980s by the Forest Products Research Station in Madison, Wisconsin. The brief result was to show that any finish is about as good as any other for what they referred to as “Moisture Excluding Effectiveness.” One coat was also about as good as three. I have sealed drawers with shellac many times. I think you will get along fine. Be sure to sand those drawers as smooth as a new baby’s skin! I used a nylon stocking as my “Inspector” tool. After all, I didn’t want my customers snagging theirs on my work!

Chris Marshall: Shellac is also a good choice for those drawer interiors because it won’t impart a lingering odor after it dries. Tung oil and other oil-based finishes tend to have a smell to them for quite some time after they cure. You don’t notice it so much on open surfaces that get plenty of air circulating around them, but close a drawer that’s freshly finished with an oil-based product, then open it and take a whiff, and you’ll see what I mean. I’ll make one suggestion about shellac, too: if it’s a new finish for you, practice first before applying it to those drawers. The first coat is easy, but brushing or wiping on multiple coats can lead to a sticky situation and brush lines, because each new coat of shellac partially dissolves the coat underneath. Polyurethane doesn’t do that.